can also be 'purchased' as correct answer
Yes. It is a fancier way of saying "bought", though. We often translate it as "приобрёл".
Две... would someone explain why this and not два, пожалуйста?
Because лампа is feminine. When it's a feminine word, две is used instead of два.
Because две it is for feminine, - лампа
Купили? With only a single purchaser?